linux-kernel - [tip:x86/asm] thread_info: Use unsigned long for flags

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Message-ID: <tip-907241dccb4ce5d9413cf3c030b32b0cfc184914@git.kernel.org>
Date:   Sat, 24 Sep 2016 09:28:58 -0700
From:   tip-bot for Mark Rutland <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     akpm@...ux-foundation.org, tglx@...utronix.de,
        mark.rutland@....com, brgerst@...il.com,
        linux-kernel@...r.kernel.org, peterz@...radead.org, hpa@...or.com,
        torvalds@...ux-foundation.org, bp@...en8.de, mingo@...nel.org,
        keescook@...omium.org, jpoimboe@...hat.com, luto@...nel.org,
        dvlasenk@...hat.com
Subject: [tip:x86/asm] thread_info: Use unsigned long for flags

Commit-ID:  907241dccb4ce5d9413cf3c030b32b0cfc184914
Gitweb:     http://git.kernel.org/tip/907241dccb4ce5d9413cf3c030b32b0cfc184914
Author:     Mark Rutland <mark.rutland@....com>
AuthorDate: Fri, 23 Sep 2016 18:24:07 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Sat, 24 Sep 2016 09:35:06 +0200

thread_info: Use unsigned long for flags

The generic THREAD_INFO_IN_TASK definition of thread_info::flags is a
u32, matching x86 prior to the introduction of THREAD_INFO_IN_TASK.

However, common helpers like test_ti_thread_flag() implicitly assume
that thread_info::flags has at least the size and alignment of unsigned
long, and relying on padding and alignment provided by other elements of
task_struct is somewhat fragile. Additionally, some architectures use
more that 32 bits for thread_info::flags, and others may need to in
future.

With THREAD_INFO_IN_TASK, task struct follows thread_info with a long
field, and thus we no longer save any space as we did back in commit:

  affa219b60a11b32 ("x86: change thread_info's flag field back to 32 bits")

Given all this, it makes more sense for the generic thread_info::flags
to be an unsigned long.

In fact given <linux/thread_info.h> contains/uses the helpers mentioned
above, BE arches *must* use unsigned long (or something of the same size)
today, or they wouldn't work.

Make it so.

Signed-off-by: Mark Rutland <mark.rutland@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1474651447-30447-1-git-send-email-mark.rutland@arm.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 include/linux/thread_info.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index e2d0fd8..45f004e 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -15,7 +15,7 @@ struct compat_timespec;
 
 #ifdef CONFIG_THREAD_INFO_IN_TASK
 struct thread_info {
-	u32			flags;		/* low level flags */
+	unsigned long		flags;		/* low level flags */
 };
 
 #define INIT_THREAD_INFO(tsk)			\